Herd Immunity Meaning: Here’s What It Means and How to Use It

Do you know what herd immunity means? This article will tell you everything that you need to know about the meaning of herd immunity. 

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With the coronavirus pandemic sweeping over the nation, you’ve probably heard a lot about the immune system lately. That said, do you know what herd immunity means? Or how it’s different from active immunity

Not to worry — this guide will tell you everything you need to know about herd immunity, including what it is and how it’s achieved. Let’s get started!

What Is the Definition of Herd Immunity?

Throughout the emergence of SARS-CoV-2 and all of its new variants, you have likely heard the term Herd Immunity, but what exactly does this type of immunity to infectious disease mean? 

Herd Immunity is a type of indirect protection or immunity to a particular disease, illness, or infection. Herd immunity is sometimes referred to as community immunity, group protection, herd protection, and population immunity. 

Herd protection can work against the spread of various diseases. It works for several reasons. For example, most of us are vaccinated against rubella (MMR), mumps, and measles before the age of two in the United States. 

By decreasing viral circulation and simply lowering the chance someone who is unvaccinated may encounter the disease, we have been able to control various contagious diseases such as:

  • Smallpox
  • Chickenpox
  • Tetanus
  • Hepatitis B
  • Rubella
  • Diphtheria
  • Whooping cough (pertussis)
  • Hepatitis A
  • Hib
  • Rotavirus
  • Polio
  • Pneumococcal disease

However, there are also various reasons why it does not work under certain conditions — so how does herd protection work?

How Does Herd Immunity Work?

Many bacterial and viral infections are spread through a chain; from person to person, these infections are transmitted. When a large portion of a population cannot transmit or even get the disease, herd immunity is in full effect, working to break down that chain, slowing or often stopping the spread of the disease.

Group protection truly helps those with lower functioning immune systems or unvaccinated people. Group protection also helps those that, due to certain circumstances, may develop an infection easier such as:

  • Young children
  • Those with underlying health conditions
  • Pregnant women
  • Others with a weakened immune system
  • Newborns; babies, infants, etc.
  • Elderly adults

Herd Immunity and COVID-19

There are a few key ways to prevent yourself and your peers from potentially transmitting or contracting the virus that causes COVID-19 (SARS-CoV-2), such as:

  • Rapid testing before gatherings;
  • Frequently washing hands 
  • Properly wearing masks
  • Vaccinations
  • Physically distancing during gatherings

That being said, herd immunity may not be the best practice for stopping the spread of the new coronavirus and its variants, Omicron and Delta. 

Doctors simply don’t know why some of those who have contracted SARS-CoV-2 have severe conditions while others have mild conditions. Some other reasons include:

  • Older adults and those with weakened immunity or chronic health conditions could become extremely ill once exposed to the virus.
  • In severe cases, people who develop COVID-19 can experience side effects that ultimately lead to death.
  • Healthcare systems and hospitals can quickly be overburdened if the masses were to contract the disease simultaneously. 

Related Words You Should Know

On your journey to learn all things “herd immunity” related, there are quite a few different terms and words that you will run into. With all these various terms, things can get a little confusing. To keep confusion to a minimum, we have a few of the most common terms and their definitions listed below: 

  • Crown Immunity or Sovereign Immunity: A legal doctrine that prevents all departments, agencies, or even political subdivisions of the government from being sued without consent
  • Congressional Immunity: Given to politicians to protect them from certain laws 
  • T Cells: Developed from stem cells, these white blood cells are a key part of our immune system
  • Natural Immunity or Innate Immunity: Immunity to an illness you were born with
  • Active Immunity or Adaptive Immunity: A type of immunity that actively develops and often adapts over time
  • Immunology: The study of all types of immune systems often an allergist will also be referred to as an immunologist 
  • B Cells: White blood cells in charge of producing antibodies 
  • Pathogen: Refers to any orgasm that can cause a disease or illness
  • Pandemic: A term used to describe the worldwide spread of an illness
  • Antigen: Refers to a substance that forces the human body to make an immune response against itself


In conclusion, population immunity, community immunity, or herd immunity refers to the ability to repel an illness or infectious disease by a large population.

Herd immunity can be created through vaccination, previous exposure to the illness, or natural immunity. When enough people are vaccinated, it helps protect society and creates herd immunity.


  1. Herd Immunity | Britannica
  2. Herd Immunity | Cambridge English Dictionary
  3. Definition of Herd Immunity | NCI Dictionary of Cancer Terms
  4. Coronavirus isease (COVID-19) | WHO